/usr/lib/x86_64-linux-gnu/libmusicbrainz5.so is in libmusicbrainz5-dev 5.1.0+git20150707-5.
This file is owned by root:root, with mode 0o777.
It is a symlink to /usr/lib/x86_64-linux-gnu/libmusicbrainz5.so.2
/usr/lib/x86_64-linux-gnu/libmusicbrainz5.so.2